Lactic Acid 500ml 85-90%
Lactic acid is an organic acid. It has a molecular formula CH3CH(OH)COOH. It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natural sources. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group. It is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries. The conjugate base of lactic acid is called lactate. The name of the derived acyl group is lactoyl.
In solution, it can ionize by loss of a proton to produce the lactate ion CH3CH(OH)CO−2. Compared to acetic acid, its pKa is 1 unit less, meaning lactic acid is ten times more acidic than acetic acid. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group.
Lactic acid is chiral, consisting of two enantiomers. One is known as l-lactic acid, (S)-lactic acid, or (+)-lactic acid, and the other, its mirror image, is d-lactic acid, (R)-lactic acid, or (−)-lactic acid. A mixture of the two in equal amounts is called dl-lactic acid, or racemic lactic acid. Lactic acid is hygroscopic. dl-Lactic acid is miscible with water and with ethanol above its melting point, which is about 16 to 18 °C. d-Lactic acid and l-lactic acid have a higher melting point. Lactic acid produced by fermentation of milk is often racemic, although certain species of bacteria produce solely d-lactic acid. On the other hand, lactic acid produced by anaerobic respiration in animal muscles has the (l) enantiomer and is sometimes called “sarcolactic” acid, from the Greek “sarx” for flesh.
In animals, l-lactate is constantly produced from pyruvate via the enzyme lactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise. It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including monocarboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues. The concentration of blood lactate is usually 1–2 mM at rest, but can rise to over 20 mM during intense exertion and as high as 25 mM afterward. In addition to other biological roles, l-lactic acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA1), which is a Gi/o-coupled G protein-coupled receptor (GPCR).
In industry, lactic acid fermentation is performed by lactic acid bacteria, which convert simple carbohydrates such as glucose, sucrose, or galactose to lactic acid. These bacteria can also grow in the mouth; the acid they produce is responsible for the tooth decay known as caries. In medicine, lactate is one of the main components of lactated Ringer’s solution and Hartmann’s solution. These intravenous fluids consist of sodium and potassium cations along with lactate and chloride anions in solution with distilled water, generally in concentrations isotonic with human blood. It is most commonly used for fluid resuscitation after blood loss due to trauma, surgery, or burns.
Swedish chemist Carl Wilhelm Scheele was the first person to isolate lactic acid in 1780 from sour milk. The name reflects the lact- combining form derived from the Latin word lac, which means milk. In 1808, Jöns Jacob Berzelius discovered that lactic acid (actually l-lactate) also is produced in muscles during exertion. Its structure was established by Johannes Wislicenus in 1873.
In 2006, global production of lactic acid reached 275,000 tonnes with an average annual growth of 10%.
Lactic acid is produced industrially by bacterial fermentation of carbohydrates, or by chemical synthesis from acetaldehyde. In 2009, lactic acid was produced predominantly (70–90%) by fermentation. Production of racemic lactic acid consisting of a 1:1 mixture of d and l stereoisomers, or of mixtures with up to 99.9% l-lactic acid, is possible by microbial fermentation. Industrial scale production of d-lactic acid by fermentation is possible, but much more challenging.
Fermented milk products are obtained industrially by fermentation of milk or whey by Lactobacillus bacteria: Lactobacillus acidophilus, Lacticaseibacillus casei (Lactobacillus casei), Lactobacillus delbrueckii subsp. bulgaricus (Lactobacillus bulgaricus), Lactobacillus helveticus, Lactococcus lactis , Bacillus amyloliquofaciens, and Streptococcus salivarius subsp. thermophilus (Streptococcus thermophilus).
As a starting material for industrial production of lactic acid, almost any carbohydrate source containing C5 and C6 sugars can be used. Pure sucrose, glucose from starch, raw sugar, and beet juice are frequently used. Lactic acid producing bacteria can be divided in two classes: homofermentative bacteria like Lactobacillus casei and Lactococcus lactis, producing two moles of lactate from one mole of glucose, and heterofermentative species producing one mole of lactate from one mole of glucose as well as carbon dioxide and acetic acid/ethanol.
Racemic lactic acid is synthesized industrially by reacting acetaldehyde with hydrogen cyanide and hydrolysing the resultant lactonitrile. When hydrolysis is performed by hydrochloric acid, ammonium chloride forms as a by-product; the Japanese company Musashino is one of the last big manufacturers of lactic acid by this route. Synthesis of both racemic and enantiopure lactic acids is also possible from other starting materials (vinyl acetate, glycerol, etc.) by application of catalytic procedures.